Spool activated lock-out valve for a hydraulic actuator load check valve

Abstract

A check valve system controls the flow of fluid between a spool valve and a hydraulic actuator and includes a pilot operated check valve that is controlled by a lock-out valve. The check valve has a poppet that engages and disengages a first valve seat in response to a pressure in a control chamber. The lock-out valve has an inlet connected to the control chamber, an outlet connected to an opening in the bore of the spool valve, and an second valve seat between the inlet and the outlet. A valve member that selectively engages and disengages the second valve seat and spool of the spool valve applies force to the valve member which responds by moving into engagement with the second valve seat. Thus in one position, the spool valve maintains the lock-out valve closed which traps pressure in the control chamber which tend to keep the check valve closed.

1. A check valve system for a hydraulic valve assembly which has a primary valve with a control element that moves to control flow of fluid to a hydraulic actuator, said check valve system comprising:
 a check valve having a poppet that engages and disengages a first valve seat to control flow of fluid between the primary valve and the hydraulic actuator, and having a control chamber with pressure therein controlling movement of the poppet; and 
 a lock-out valve having an inlet in fluid communication with the control chamber and an outlet with an second valve seat between the inlet and the outlet, the lock-out valve comprising a valve member that selectively engages and disengages the second valve seat, wherein the control element applies non-hydraulic force to the valve member which responds by moving into engagement with the second valve seat. 
 
     
     
       2. The check valve system as recited in  claim 1  wherein the control element is a valve spool that moves within a spool bore; and the lock-out valve is located in the spool bore at one end of the valve spool. 
     
     
       3. The check valve system as recited in  claim 2  wherein the outlet of the lock-out valve is connected to an opening in the spool bore. 
     
     
       4. The check valve system as recited in  claim 1  wherein the lock-out valve further comprises a spring biasing the valve member away from the second valve seat. 
     
     
       5. The check valve system as recited in  claim 1  wherein the valve member comprises a valve element that selectively engages and disengages the second valve seat, a shaft contacting the valve element, and a retainer coupled to the shaft, wherein the control element applies force to the retainer. 
     
     
       6. The check valve system as recited in  claim 1  wherein the valve member comprises a valve element that selectively engages and disengages the second valve seat, a shaft having a first end engaging the valve element and having a second end, and a retainer mounted on the shaft adjacent the second end, wherein the control element applies force to the retainer. 
     
     
       7. The check valve system as recited in  claim 6  wherein the lock-out valve further comprises:
 a first spring biasing the valve member away from the second valve seat; and 
 a second spring biasing the retainer along the shaft toward the second end. 
 
     
     
       8. The check valve system as recited in  claim 7  wherein the lock-out valve further comprises a third spring biasing the valve element toward the second valve seat. 
     
     
       9. The check valve system as recited in  claim 1  wherein the poppet of the check valve defines a fluid channel between the control chamber and a workport that is provided in the hydraulic valve assembly for connection to the hydraulic actuator. 
     
     
       10. The check valve system as recited in  claim 1  wherein the poppet of the check valve is biased toward the first valve seat by a check valve spring. 
     
     
       11. A check valve system for a hydraulic valve assembly which has a valve spool that slides within a spool bore to control flow of fluid through a passage to a workport, said check valve system comprising:
 a check valve within the passage and having a poppet that engages and disengages a first valve seat to control flow of fluid between the spool bore and the workport, and having a control chamber a side of the poppet that is remote from the first valve seat; and 
 a lock-out valve having an inlet connected to the control chamber and an outlet connected to an opening in the spool bore with an second valve seat between the inlet and the outlet, the lock-out valve comprising: 
 (a) a valve element that selectively engages and disengages the second valve seat, 
 (b) a shaft having a first end section in contact with the valve element and having a second end, 
 (c) a retainer coupled to the shaft, wherein the valve spool applies force to the retainer that tends to move the valve element into engagement with the second valve seat, 
 (d) a first spring biasing the shaft away from the valve element; and 
 (e) a second spring biasing the retainer with respect to the shaft and toward the second end. 
 
     
     
       12. The check valve system as recited in  claim 11  wherein the lock-out valve is located in the spool bore at one end of the valve spool. 
     
     
       13. The check valve system as recited in  claim 11  wherein the lock-out valve further comprises a third spring biasing the valve element toward the second valve seat. 
     
     
       14. The check valve system as recited in  claim 11  wherein the poppet of the check valve defines a fluid channel between the control chamber and the passage to the workport. 
     
     
       15. The check valve system as recited in  claim 11  wherein the poppet of the check valve is biased toward the first valve seat by a check valve spring. 
     
     
       16. In a hydraulic valve assembly which has a valve spool that slides within a spool bore to control flow of fluid to a workport, a check valve system comprising:
 a check valve located in a passage between the spool bore and the workport and having a poppet that engages and disengages a first valve seat to control flow of fluid in the passage, and having a control chamber on a remote side of the poppet from the first valve seat; and 
 a lock-out valve comprising: 
 (a) a cartridge with an inlet in fluid communication with the control chamber and an outlet connected to an opening in the spool bore, and having an second valve seat between the inlet and the outlet, 
 (b) a valve element moveable within the cartridge to selectively engage and disengage the second valve seat, 
 (c) a shaft having a first end and a second end, wherein the first end engages the valve element, 
 (d) a retainer mounted on the shaft, wherein the valve spool engages the retainer to apply force that tends to move the valve element into engagement with the second valve seat, 
 (e) a first spring engaging the cartridge and biasing the retainer away from the cartridge to enable the valve element to disengage from the second valve seat; and 
 (f) a second spring biasing the shaft with respect to the retainer and toward the second valve seat. 
 
     
     
       17. The check valve system as recited in  claim 16  wherein the cartridge of the lock-out valve is located in the spool bore at one end of the valve spool. 
     
     
       18. The check valve system as recited in  claim 16  wherein the lock-out valve further comprises a third spring biasing the valve element toward the second valve seat. 
     
     
       19. The check valve system as recited in  claim 16  wherein the poppet of the check valve includes a fluid channel therein which provides fluid communication between the control chamber and the workport. 
     
     
       20. The check valve system as recited in  claim 16  wherein the poppet of the check valve is biased toward the first valve seat by a check valve spring.